Mark P.M. Harms

Incidence and hemodynamic characteristics of near-fainting in healthy 6- to 16-year old subjects

OBJECTIVES We studied the incidence and hemodynamic characteristics of near-fainting under orthostatic stress in healthy children and teenagers. BACKGROUND Orthostatic stress testing is increasingly used to identify young subjects with unexplained syncope. However, the associated incidence of syncope and hemodynamic responses in normal young subjects are not well known. METHODS Eighty-four healthy subjects 6 to 16 years old performed forced breathing, stand-up and 70 degrees tilt-up tests. An intravenous line to sample blood for biochemical assessment of sympathetic function was introduced between the stand-up and tilt-up tests. Finger arterial pressure was measured continuously. Left ventricular stroke volume was computed from the pressure pulsations. RESULTS Sixteen of the 84 subjects were excluded because of technical problems. The incidence of a near-fainting response in the remaining 68 subjects was 10% (7 of 68) for the stand-up test and 40% (29 of 68) for the tilt-up test. Baseline parasympathetic and sympathetic activity of nonfainting and near-fainting subjects was not different. Near-fainting was characterized by attenuated systemic vasoconstriction and exaggerated tachycardia that occurred as early as 1 min after return to the upright position. On tilt-up, plasma adrenaline levels increased by a factor of 2, with slightly higher increments in the near-fainting subjects. CONCLUSIONS Inadequate vasoconstriction is the common underlying mechanism of near-fainting in young subjects. The remarkably high incidence of near-fainting during the tilt-up test after intravascular instrumentation raises serious doubts about the utility of this procedure in evaluating syncope of unknown origin in young subjects.

Reconstruction of brachial pressure from finger arterial pressure during orthostasis

Introduction In patients with recurrent syncope, monitoring of intra-arterial pressure during orthostatic stress testing is recommended because of the potentially sudden and rapid development of hypotension. Replacing brachial arterial pressure (BAP) by the non-invasively obtained finger arterial pressure (FinAP) has advantages because catheterization in itself may provoke a syncope. Objective To investigate whether reconstruction of the brachial pressure curve (ReBAP) from FinAP can account for systolic and diastolic offset in the recorded pressure on the transition from a supine to an upright position and during maintained postural stress. Methods In nine healthy young subjects BAP and FinAP were recorded in the supine position, during 8 min of standing and during 20 min of 70° passive head-up tilt (HUT70) whereafter three of the subjects fainted within 20 min of HUT. The FinAP signal was modeled off-line into a reconstructed brachial pressure curve. Results For FinAP but not for ReBAP, systolic (P < 0.05) and diastolic (P < 0.001) bias increased in the transition from the supine to the HUT position. Bias for the systolic pressure in the supine position and after 7.5 and 20 min of HUT were 2, 7 and 11 mmHg for FinAP but only 0, −2 and 1 mmHg for ReBAP (P < 0.05 for HUT). For the diastolic pressure these values were −2, 5 and 8 mmHg for FinAP and 4, 5 and 6 for ReBAP (P < 0.01 for supine). Conclusions Brachial pressure reconstruction from the finger arterial pressure waveform accounts for the bias from the supine to the upright position, eliminates the bias for the systolic but not for diastolic finger pressure and reduces the trend in diastolic bias with increased tilt duration.

Prospective evaluation of non-pharmacological treatment in vasovagal syncope

AIMS Initial treatment of vasovagal syncope (VVS) consists of assuring an adequate fluid and salt intake, regular exercise and application of physical counterpressure manoeuvres. We examined the effects of this non-pharmacological treatment in patients with frequent recurrences. METHODS AND RESULTS One hundred patients with > or =3 episodes of VVS in the 2 years prior to the start of the study openly received non-pharmacological treatment. We evaluated this treatment both with respect to syncopal recurrences, factors associated with recurrence, and quality of life (QoL). The median number of syncopal recurrences was lower in the first year of non-pharmacological treatment compared with the last year before treatment (median 0 vs. 3; P < 0.001), but 49% of patients experienced at least one recurrence. In multivariable analysis, a higher syncope burden prior to inclusion was significantly associated with syncopal recurrence. Disease-specific QoL improved over time, with larger improvements for patients with more reduction in syncope burden. CONCLUSION In patients with frequent recurrences of VVS, non-pharmacological treatment has a beneficial effect on both syncopal recurrence and QoL, but nearly half of these patients still experience episodes of syncope.

Effects of aging on the cerebrovascular orthostatic response

When healthy subjects stand up, it is associated with a reduction in cerebral blood velocity and oxygenation although cerebral autoregulation would be considered to prevent a decrease in cerebral perfusion. Aging is associated with a higher incidence of falls, and in the elderly falls may occur particularly during the adaptation to postural change. This study evaluated the cerebrovascular adaptation to postural change in 15 healthy younger (YNG) vs. 15 older (OLD) subjects by recordings of the near-infrared spectroscopy-determined cerebral oxygenation (cO₂Hb) and the transcranial Doppler-determined mean middle cerebral artery blood velocity (MCA V(mean)). In OLD (59 (52-65) years) vs. YNG (29 (27-33) years), the initial postural decline in mean arterial pressure (-52 ± 3% vs. -67 ± 3%), cO₂Hb (-3.4 ± 2.5 μmoll(-1) vs. -5.3 ± 1.7 μmoll(-1)) and MCA V(mean) (-16 ± 4% vs. -29 ± 3%) was smaller. The decline in MCA V(mean) was related to the reduction in MAP. During prolonged orthostatic stress, the decline in MCA V(mean)and cO(2)Hb in OLD remained smaller. We conclude that with healthy aging the postural reduction in cerebral perfusion becomes less prominent.

Treatment of vasovagal syncope: pacemaker or crossing legs?

A 50-year-old male patient continued to experience syncope after implantation of a pacemaker. During cardiovascular examination, the patient showed a typical vasovagal response, with normal pacemaker function. Leg crossing, which prohibits the pooling of blood in the legs and abdomen, at the onset of symptoms helped to prevent this response. The authors recommend a course of leg crossing as a measure to treat vasovagal syncope.

Central and cerebrovascular effects of leg crossing in humans with sympathetic failure

Leg crossing increases arterial pressure and combats symptomatic orthostatic hypotension in patients with sympathetic failure. This study compared the central and cerebrovascular effects of leg crossing in patients with sympathetic failure and healthy controls. We addressed the relationship between MCA Vmean (middle cerebral artery blood velocity; using transcranial Doppler ultrasound), frontal lobe oxygenation [O2Hb (oxyhaemoglobin)] and MAP (mean arterial pressure), CO (cardiac output) and TPR (total peripheral resistance) in six patients (aged 37–67 years; three women) and age- and gender-matched controls during leg crossing. In the patients, leg crossing increased MAP from 58 (42–79) to 72 (52–89) compared with 84 (70–95) to 90 (74–94) mmHg in the controls. MCA Vmean increased from 55 (38–77) to 63 (45–80) and from 56 (46–77) to 64 (46–80) cm/s respectively (P<0.05), with a larger rise in O2Hb [1.12 (0.52–3.27)] in the patients compared with the controls [0.83 (−0.11 to 2.04) μmol/l]. In the control subjects, CO increased 11% (P<0.05) with no change in TPR. By contrast, in the patients, CO increased 9% (P<0.05), but also TPR increased by 13% (P<0.05). In conclusion, leg crossing improves cerebral perfusion and oxygenation both in patients with sympathetic failure and in healthy subjects. However, in healthy subjects, cerebral perfusion and oxygenation were improved by a rise in CO without significant changes in TPR or MAP, whereas in patients with sympathetic failure, cerebral perfusion and oxygenation were improved through a rise in MAP due to increments in both CO and TPR.

Noninvasive beat-to-beat finger arterial pressure monitoring during orthostasis: a comprehensive review of normal and abnormal responses at different ages

Over the past 30 years, noninvasive beat‐to‐beat blood pressure (BP) monitoring has provided great insight into cardiovascular autonomic regulation during standing. Although traditional sphygmomanometric measurement of BP may be sufficient for detection of sustained orthostatic hypotension, it fails to capture the complexity of the underlying dynamic BP and heart rate responses. With the emerging use of noninvasive beat‐to‐beat BP monitoring for the assessment of orthostatic BP control in clinical and population studies, various definitions for abnormal orthostatic BP patterns have been used. Here, age‐related changes in cardiovascular control in healthy subjects will be reviewed to define the spectrum of the most important abnormal orthostatic BP patterns within the first 180 s of standing. Abnormal orthostatic BP responses can be defined as initial orthostatic hypotension (a transient systolic BP fall of >40 mmHg within 15 s of standing), delayed BP recovery (an inability of systolic BP to recover to a value of >20 mmHg below baseline at 30 s after standing) and sustained orthostatic hypotension (a sustained decline in systolic BP of ≥20 mmHg occurring 60–180 s after standing). In the evaluation of patients with light‐headedness, pre(syncope), (unexplained) falls or suspected autonomic dysfunction, it is essential to distinguish between normal cardiovascular autonomic regulation and these abnormal orthostatic BP responses. The prevalence, clinical relevance and underlying pathophysiological mechanisms of these patterns differ significantly across the lifespan. Initial orthostatic hypotension is important for identifying causes of syncope in younger adults, whereas delayed BP recovery and sustained orthostatic hypotension are essential for evaluating the risk of falls in older adults.

Orthostatic Hypotension in the First Minute After Standing Up: What Is the Clinical Relevance and Do Symptoms Matter?

See related article, pp 946–954 After 1980, techniques became available to monitor rapid hemodynamic changes continuously and noninvasively.1 These extraordinary scientific developments enabled clinicians and researchers at the end of the 20th century to noninvasively study the physiological mechanisms underlying the transient fall in blood pressure (BP) that occurs in the first 30 s of standing. TILDA (The Irish Longitudinal Study on Ageing), a large prospective randomly selected population-based study of over 8000 community-dwelling adults aged >50 years, has shown that an impaired recovery of BP after the initial fall is associated with long-term adverse cardiovascular health outcomes (see later).2 In this issue of Hypertension , the longitudinal association between symptomatic orthostatic hypotension (OH) at 30 s of standing and the occurrence of incident late-life depression in the TILDA cohort is reported.3 In this editorial commentary, we address the clinical and prognostic significance of symptomatic OH in the first 30 s after standing up because of impaired orthostatic BP recovery patterns and incident late-life depression. For this, we will focus first on the classification and pathophysiology of short-term (first 180 s) orthostatic adjustments because it is important to ground observational associations in physiology. It is useful to classify the short-term orthostatic circulatory response on active standing in 1. the initial response (first 30 s) and 2. the early phase of stabilization (30–180 s).2 Details of the physiological mechanisms underlying the typical transient fall in BP that occurs in the first minute of standing in healthy subjects (Figure, top) …

Orthostatic blood pressure recovery patterns in suspected syncope in the emergency department

Introduction Orthostasis is a frequent trigger for (pre)syncope but some forms of orthostatic (pre)syncope have a worse prognosis than others. Routine assessment of orthostatic BP in the ED can detect classic orthostatic hypotension, but often misses these other forms of orthostatic (pre)syncope. This study aimed to determine the frequency of abnormal orthostatic BP recovery patterns in patients with (pre)syncope by using continuous non-invasive BP monitoring. Methods We performed a prospective cohort study in suspected patients with (pre)syncope in the ED of a tertiary care teaching hospital between January and August 2014. Orthostatic BP was measured during the active lying-to-standing test with Nexfin, a continuous non-invasive finger arterial pressure measurement device. Orthostatic BP recovery patterns were defined as normal BP recovery, initial orthostatic hypotension, delayed BP recovery, classic orthostatic hypotension and reflex-mediated hypotension. Results Of 116 patients recruited, measurements in 111 patients (age 63 years, 51% male) were suitable for analysis. Classic orthostatic hypotension was the most prevalent abnormal BP pattern (19%), but only half of the patients received a final diagnosis of orthostatic hypotension. Initial orthostatic hypotension and delayed BP recovery were present in 20% of the patients with (pre)syncope of whom 45% were diagnosed as unexplained syncope. Reflex-mediated hypotension was present in 4% of the patients. Conclusion Continuous non-invasive BP measurement can potentially identify more specific and concerning causes of orthostatic (pre)syncope. Correct classification is important because of different short-term and long-term clinical implications.

Ultrasound and NICOM in the assessment of fluid responsiveness in patients with mild sepsis in the emergency department: a pilot study

Objective We investigated whether combining the caval index, assessment of the global contractility of the heart and measurement of stroke volume with Noninvasive Cardiac Output Monitoring (NICOM) can aid in fluid management in the emergency department (ED) in patients with sepsis. Setting A prospective observational single-centre pilot study in a tertiary care centre. Primary and secondary outcomes Ultrasound was used to assess the caval index, heart contractility and presence of B-lines in the lungs. Cardiac output and stroke volume were monitored with NICOM. Primary outcome was increase in stroke volume after a fluid bolus of 500 mL, while secondary outcome included signs of fluid overload. Results We included 37 patients with sepsis who received fluid resuscitation of at least 500 mL saline. The population was divided into patients with a high (>36.5%, n=24) and a low caval index (<36.5%, n=13). We observed a significant increase (p=0.022) in stroke volume after 1000 mL fluid in the high caval index group in contrast to the low caval index group but not after 500 mL of fluid. We did not find a significant association between global contractility of the left ventricle and the response on fluid therapy (p=0.086). No patient showed signs of fluid overload. Conclusions Our small pilot study suggests that at least 1000 mL saline is needed to induce a significant response in stroke volume in patients with sepsis and a high caval index. This amount seems to be safe, not leading to the development of fluid overload. Therefore, combining ultrasound and NICOM is feasible and may be valuable tools in the treatment of patients with sepsis in the ED. A larger trial is needed to confirm these results.